The present invention is a storm water filter system for filtering floatable debris and non-floating pollutants from storm water passing through a storm water drain system and more specifically, the present invention is directed towards a storm water filtering system having a floatable skimmer therein for capturing floatable debris and trash from the storm water and separate filtration of non-floatable pollutants from water passing therethrough.
Federal clean water requirements require that water bodies such as lakes and rivers meet strict minimal water quality specifications. To achieve this end, storm water drainage pipes often require treatment before conveying storm water into receiving water bodies. As a result, a wide variety of technologies have been developed to treat storm water and improve the water quality.
A common variety of storm water treatment systems are hydrodynamic separators such as baffle boxes and vortex systems. Hydrodynamic separators can treat relatively large water flows and are good for removing solids that are relatively large in size. Hydrodynamic separators do very little to remove the dissolved pollutants and have a typically poor removal efficiency for fine particles.
To achieve water treatment beyond what can be accomplished by a hydrodynamic separator, another class of storm water treatment systems commonly referred to as filtration systems are used. Filtration systems typically will pass the water flow through a filter media such as sand, zeolite, activated carbon, and the like. Filter media is typically selected to do more than remove solids from the water flow. Depending on the pollutants of concern, filter media can be selected to remove specific dissolved pollutants such as nutrients, metals, or a wide variety of chemical contaminates. However, a problem with using filter media in a storm water treatment system is the significant influence of friction between the water and the media. In addition, changing the direction of water flow as it passes through a filtration system reduces the kinetic energy of the water flow which will reduce the volume water flow. During big rain events a storm water filtration system in a storm water pipe can significantly inhibit the passage of water and cause flooding upstream from the filtration system. If the filtration system becomes clogged with debris the water flow can be completely stopped.
The purpose of the present invention is to be able to treat the storm water flow with a storm water filtration system that is resistant to clogging, yet be able to pass large water flows during large rain events. In this way filter media can be incorporated into the treatment of storm water without the potential of flooding upstream caused by the filtration system. The invention can be described as a vault that contains a floating skimmer system with an up-flow filtration system. The skimmer system portion of the invention will be positioned in line with the water flow and will divert the water flow through the filtration system. The water flow will then flow through the filter where it is treated by the media. Once the water flow has passed through the filter it will continue down stream. During large rain events that cause the water levels within the invention to rise, the floating skimmer will also rise and allow water to flow under the skimmer and by-pass the filter by-pass the filtration treatment.
The invention has two primary components that work in concert with each other. The floating skimmer system acts to direct the water flow down toward the underside of the skimmer and through the filter during low to medium flow rates. During large flow rates the floating skimmer reacts to allow the high flow rates to pass straight ahead through the vault with minimal friction. The up-flow filter provides treatment to the water flow during low to medium flow rates and is resistant to clogging due to its design and nature.
In the present invention a relative short floating skimmer is used and has the same performance of a much taller fixed skimmer without the head loss associated with a taller skimmer by opening up a larger passageway under the skimmer. A storm water treatment structure that makes use of a floating skimmer can be more easily retrofitted to an existing water shed storm drain system due to the minimal head loss of the shorter skimmer.
In my prior U.S. Pat. No. 6,869,525 for a Storm Drain Filter System I show a storm drain filter system which includes a skimmer for collecting floating hydrocarbons and for absorbing the hydrocarbons in a hydrocarbon absorbing boom while preventing them from passing out of the skimmer. In my prior U.S. Pat. No. 7,294,256 for a Storm Water Filter System, a storm water filter system is provided for filtering storm water being fed into an in-ground well and uses a fixed skimmer to prevent floating organic debris from entering the discharge into the in-ground recharge well.